On Jan. 11, 1991, recommendations of Immunization Practices Advisory Committee (ACIP) for routine Hib vaccination for infants beginning at 2 months of age were published in MMWR.

Hib disease used to be common in the U.S. and about 20,000 children got serious Hib infections every year. Thanks to the vaccine, serious cases of Hib disease have dropped by more than 99% since 1991.